The present invention relates to a felt for papermaking machines and more particularly to a non-woven felt for use in the wet press section of a papermaking machine.
The prior art includes a number of attempts to provide a construction particularly suitable for use in the wet press section of a papermaking machine. In the construction of a wet press felt, the desirability of maintaining a controlled void volume within the felt has been recognized. In use, loss of void volume due to compaction of wet press felts upon repeated passes through the nip of the wet press rollers is common. The compaction of the wet press felt shortens the useful life of the felt by limiting the drainage of water thrugh the felt. This also reduces the efficiency of the paperamaking machine.
Typical prior art wet press felts include a woven fabric base to which is needled a batt material. See for example the descriptions given in U.S. Pat. Nos. Re. 21,890; 2,581,790; 3,059,312; 3,086,276; 3,928,699; 4,356,225, 4,427,734; 4,529,643 and 4,565,735.
In U.S. Pat. No. 4,427,734, a wet pressed felt comprising a woven base, layers of mesh fabric and layers of non-woven batt material is disclosed. The layers of mesh fabric are interposed between layers of batt material. The layers of mesh fabric and batt material are needled to a base fabric of interwoven textile yarns.
U.S. Pat. No. 4,356,225 discloses a wet press felt which comprises a woven base with batts needled thereto in which a three ply weave pattern of the woven base results in an improved void volume and increased fabric stability.
The construction of a wet press felt which includes a woven base with batts needled thereto is a complicated and expensive process. Wet press felt constructions which do not employ a woven fabric base have been considered. U.S. Pat. No. 3,664,905 discloses a papermaker's felt which comprises alternating layers of oriented fibers of batt material which are interconnected by needling and a blown adhesive layer.
U.S. Pat. No. 3,920,511 discloses a non-woven papermaker's felt which comprises a plurality of layers of webs formed of fibers oriented substantially longitudinally consolidated into a homogeneous mass and a web of fibers is needled thereinto.